To determine nature of point, find d2y/dx2. If it is > 0 it is minimum point. Which means y is a minimum value. If it is < 0 then it is maximum point.

The second part is Y is a decreasing function, therefore :

dy/dt<0. From there set of t can be equated. ]]>

]]>y is decreasing function of t

i.e. t = f(y)

=> dt/dy < 0

Ok ... umm ... something ... like ... that ...

But Part 2 needs *meh*?

2nd question , should do double differentiation. Replace, it with the value of t from 1st question. Determine which t, will produce the negative and that t should be the answer to the receding flood waters. ðŸ˜›

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